Herein is described a study of the frequency and familial aggregation of malignant neoplasia in Laredo, Texas, a Mexican-American community. The study will be based on the use of extensive church and civil records to construct genealogies for a large proportion of the population over several generations. Death records, by cause and age, from various sources will then be mapped onto the genealogies. This will form the basis for a genetic epidemiological study of cancer to (1) assess the degree to which common genetic relationship may predispose certain families to cancer, (2) assess the degree to which common social environment may predispose to cancer, (3) assess the relationship of fertility and offspring survivorship to cancer mortality, (4) examine the dynamic relationships between cancer and the other causes of mortality which compete with it, (5) determine risks of cancer death to newborns based on pedigree experience, and (6) develop new methodology for accomplishing all of the above.